Sylvania



Feb. 19, 1929. 1,702,428

P. N. BOSSART MICROPHONE AMPLIFIER Original Filed April 18, 1925 mi 1W INVENTORI ax-WM" fil- 'm ATTORNEY field member 1 are two U-shaped pole-meme,

Patented Feb. 19, 1929.

were stares PAUL N. IBOSSART, or SWISSVALE, PENNSYLVANIAyASSIGNOR 'ro THE'UNION SWITCH SYLVANIA.

&. SIGNAL COMPANY, OF SWISSVALE, PEN'NSYLVANIA, 'A'CORPORA TION OF-PENN- MICROPHONE AMPLIFIER- 555 Application filed April 18, 1925,1Serial No. 24,204. Reneweaiui ia ieaa,

Myinvcntion relates to microphone amplifiers, and has for an object the provision of an improved device of the vibrating armature microphone type characterized-by increased er'iiciency and sensitiveness. j

I will describe two forms of amplifiers embodying my invention, and will then point out the novel features thereof in claim.

In the accompanying drawing, ig. l is a view showing in isometrical projection one form of microphone amplifier embodying my invention. Fig. 2 is a plan view showingia modification o the amplifier shown in Fig. 1 and also embo ying my invention. 1

Referring first to Fig. 1, the operating parts of the device are mounted on a base plate 22 provided with three upstanding screws 2. These screws support a U-shaped field memher 1, which, as here shown, is a permanent magnet but may equally well be an electromagnet. Associated with the two legs of this bers 3, which are so mounted with respect to the field member that the two poles of each pole member confront the two poles of the othermember. Each pole member. 3 slides with two outside plates 4 of electrical sheet steehavhich are attached to the pole members so as to slide over the poles of the permanent magnet 1. The inner end of each of these plates is recessed to conform substantiall. y to the shape of the corresponding pole member 3. he two plates 4 associated with each pole member serve to guide the pole member as it slides, and they also serve to conduct magnetic flux between the pole member and the associated leg of the field memher 1.

The reference character 6 designates the armature of the relay, which armature is lo cated between the confronting poles of the two pole members 3. The inner end of this armature as here shown is reduced in thickness, although this reduction is not needed in all cases, and is rigidly clamped between two armature supports 7 and 8 fixed to the base plate 22. It will be seen, therefore, that the amature is free to vibrate in the spaces between the poles of the pole members 3, and that its axis of vibration is beyond the inner pair of poles of these members. The thickness of the main body of the armature 6 may, for example, be .014, whereas the thickness of the inner end of this armature may be .004.

The armature 6 is provided with a winding 20 which surrounds that portion I;

turelying betweenthe poles of the pole m'em bers 3, but which is fixed to the base plate 22 and is out of contact. with any part of, the armature. QThis' 'windingfis illustrated .diagrammatically inthe drawing, but 'in,prac.. tice it is supportedbya blockl9 which is at tached to. the base plate 22. I Each pole memberfi is provided withea pair of adjusting screws 5,.w1iich are tapped into the pole member and pass. with clearance h qug h kai thqfiddm m et .A co springifi surrounds eaehpf these -.s' new's be-. tween the pole, member andthe field 'Inember. By suitable adj ustinentjof the screws 5 ,the air gaps between the armature Giand each pole of each pole member 3;:may ibepr0perly ad justed. This adjustingifeatnre may no t.=al ways he needed, andeanbe omitted when the armature is adjustabl y connected with Ithe microphone? as hereinafter described j w, The reference charaeter' iMl designates. ,a' microphone eomprising theusualmicrophone case 2. a. m c d plmgml. a'n' e' d phragm clamping nut 10.--'-The diaphragm 11 is operativelyconneeted with thearmature 6 by means of a Y-shaped 1116111116 39 flhlleft hand endpf this rnember is attached the diaphragm clamping nut 10, and each arm of the other or forked end is threaded and passes with clearance through a hole in the armature. The armature is clamped between two nuts 25 on each arm, so that by varying the positions of these nuts the air gaps between the armature and the pole members may be varied. The parts are so adjusted that with no current in winding 20 the armature remains at rest in its mid-position between the two pairs of pole faces of pole members 3. When this adjustment is provided the pole members 3 may be fixed with respect to the permanent magnet 1, and the microphone M may be fixed to the base plate 22, thus eliminating the adjusting screws 5, and also the adjusting screw 18 hereinafter described. Furthermore, the Yshaped member 9 stiffens the armature, and prevents it from being twisted across the pole faces and sticking.

As here shown, the microphone M is fixed to a microphone support 13 which is in turn adj ustably attached to the base plate 22 by screws 16 co-operating with slots in the support 13. A microphone adjusting block 17 is attached to the base plate '22 and is provided with a horizontal hole which receives If reduces mo'tion'al lo 7 (le gigi ned for 1. greatly inerzised' a'rihature force by using ah elecfiro'iiia g'n'e't i'ns'tead of a permanent magnet for the field member 1, and the alternating current resistance of the relay may be decreased by laminating the,

n and demop BOSSART. 

